///////////////////////////////////////////////////////////////
//  Copyright 2017 John Maddock. Distributed under the Boost
//  Software License, Version 1.0. (See accompanying file
//  LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt

//
// Check results of truncated overflow.
//

#ifdef _MSC_VER
#define _SCL_SECURE_NO_WARNINGS
#endif

#include <nil/crypto3/multiprecision/cpp_int.hpp>
#include "test.hpp"
#include <boost/random/mersenne_twister.hpp>
#include <boost/random/uniform_int.hpp>

template<class T>
T generate_random(unsigned bits_wanted) {
    static boost::random::mt19937 gen;
    typedef boost::random::mt19937::result_type random_type;

    T max_val;
    unsigned digits;
    if (std::numeric_limits<T>::is_bounded && (bits_wanted == (unsigned)std::numeric_limits<T>::digits)) {
        max_val = (std::numeric_limits<T>::max)();
        digits = std::numeric_limits<T>::digits;
    } else {
        max_val = T(1) << bits_wanted;
        digits = bits_wanted;
    }

    unsigned bits_per_r_val = std::numeric_limits<random_type>::digits - 1;
    while ((random_type(1) << bits_per_r_val) > (gen.max)())
        --bits_per_r_val;

    unsigned terms_needed = digits / bits_per_r_val + 1;

    T val = 0;
    for (unsigned i = 0; i < terms_needed; ++i) {
        val *= (gen.max)();
        val += gen();
    }
    val %= max_val;
    return val;
}

template<class Number>
void test() {
    using namespace nil::crypto3::multiprecision;
    typedef Number test_type;

    for (unsigned i = 30; i < std::numeric_limits<test_type>::digits; ++i) {
        for (unsigned j = std::numeric_limits<test_type>::digits - i - 1; j < std::numeric_limits<test_type>::digits;
             ++j) {
            for (unsigned k = 0; k < 10; ++k) {
                test_type a = static_cast<test_type>(generate_random<cpp_int>(i));
                test_type b = static_cast<test_type>(generate_random<cpp_int>(j));
                test_type c = static_cast<test_type>(cpp_int(a) * cpp_int(b));
                test_type d = a * b;
                BOOST_CHECK_EQUAL(c, d);

                if ((k == 0) && (j == 0)) {
                    for (unsigned s = 1; s < std::numeric_limits<test_type>::digits; ++s)
                        BOOST_CHECK_EQUAL(a << s, test_type(cpp_int(a) << s));
                }
            }
        }
    }
}

int main() {
    using namespace nil::crypto3::multiprecision;

    test<int512_t>();
    test<uint512_t>();

    //
    // We also need to test type with "odd" bit counts in order to ensure full code coverage:
    //
    test<number<cpp_int_backend<528, 528, signed_magnitude, unchecked, void>>>();
    test<number<cpp_int_backend<528, 528, unsigned_magnitude, unchecked, void>>>();
    test<number<cpp_int_backend<48, 48, signed_magnitude, unchecked, void>>>();
    test<number<cpp_int_backend<48, 48, unsigned_magnitude, unchecked, void>>>();
    return boost::report_errors();
}
